The subject matter of the present invention comprises a two-component agent or product with a pH value that automatically changes within a time period of from 1 to 60 minutes in a time delayed fashion after mixing the two components. The two-component agent comprises one component (A) containing at least one acid and another component (B) containing at least one base. The acid and/or the base have reduced water solubility. The subject matter of the invention also includes a method of treating hair, especially a method of caring for hair or for permanent shaping of the hair.
Although most chemical, technical, food technology and cosmetic products have the same pH value from the start to finish during their usage, there have been many attempts to provide systems for certain special applications, which change their pH after application.
Different reasons can require these special applications, for example
A substance has a pH value, at which it is most effective but is only storage-stable to a limited extent;
A pH-dependent activity, which should be controlled in its time dependence;
Two pH-dependent activities, which have respective different optimum pH values following each other, in spite of only one-time application;
A reaction delay should be provided, in order to allow a previous diffusion; and
A color change should indicate the end of activity.
A method for permanent shaping is described in DE 1089124 A1, in which ammonia is released from urea with the help of urease and provides an increase in the pH during the acting time.
A composition and method are known from DE 23 49 050 A, in which waving effectiveness is continuously reduced by lowering the pH. Immediately prior to application alkali cleavable organic compounds with ester or halo groups in the molecule that produce acid when cleaved are added to the permanent shaping agent. Because of that addition the concentration of alkali during the acting time generally decreases and is in the desired range. For example, acetic acid ethyl ester and triacetin are generally suitable as the esters. An acceleration of the cleavage rate of the compounds containing the ester groups can be achieved by addition of the lipase, Pancreatin.
A system is known from DE-PS 198 60 239 C2, in which the pH behavior of the permanent wave solution changes with time because of enzymatic cleavage of esters, especially e.g. triglycerides, and simultaneous counter buffering of the pH behavior, in order to reduce the initial waving effectiveness after a brief time and also to prevent exceeding a pH of 7.0.
A system is known from DE 199 02 246 A1, in which pH is lowered by non-enzymatic hydrolysis of a sufficiently unstable lactone. The speed and end point of this non-enzymatic hydrolysis depend on the type and concentration of the concerned educt within the scope of the conditions (temperature, initial pH, etc).
Each of these systems has a serious disadvantage: If the rate of pH change is produced by enzyme-catalyzed reactions, it is extremely difficult to set (and above all to maintain) a definite course of the pH or pH-time variation. The enzymatic activity and thus the kinetics of the pH behavior changes with the storage conditions. Thus a three-component system is usually required for the foregoing reason: One component for the hair product, one component (strictly water-free) for the hydrolyzed ingredient and one for the enzyme. Additionally during application an excessive effort is necessary to mix the three components completely and homogeneously. Also performing the mixing sufficiently rapidly is troublesome and not without problem.
The spontaneous hydrolysis of the lactones disclosed in DE 199 02 246 A1 avoids the problem of enzyme catalysis; generally only a limited number of suitable compounds exist. The hydrolysis conditions for the concerned material are definitely dependent on the nature of the substance and the formulation of the components can hardly effect it, so that no noteworthy possibility exists to adjust this sort of system to different conditions or starting materials.
It is common to all the methods described here that the “normal” product mass must be mixed with “non-normal” components (water-free suspensions, crystalline or powdery substances). The expression “normal” here relates to the chemical composition and pleasing character, i.e. the color, smell, flow properties, viscosity, haptic properties.